Fast API response codes not working as expected

Question

I am trying to validate the JSON request and based on that I want to return the response code using Fast API. By default, Fast API returns 422 for validation exceptions, but I want to follow the Open API standards and as per that ideally, it should be 400 for validation exceptions. Hence, in order to achieve that, I developed something like below:

class Item(BaseModel):
    id: str
    value: str


class Message(BaseModel):
    message: str

responses = {400: {"model": Message, "description": "The item was not found"}}


@app.post("/v1/validate", response_model=Item,
          responses={**responses, 200: {"content": "valid"}})
def output_port_validate(provisioning_request: ProvisioningRequest):
    result = ApiController(dbt_provisioner).validate_request(provisioning_request)
    if result:
        return result
    else:
        return Response(status_code=400, content={"message": "Item not found"})

However, it is giving me 500 internal server error in response to the below error:

raise ResponseValidationError(
fastapi.exceptions.ResponseValidationError

I followed the official documentation but had no luck.

P.S. I have standard data classes as models, not the Pydantic ones.

Please show the **full** traceback. – Łukasz Kwieciński Jul 21 '23 at 15:22 — Łukasz Kwieciński, Jul 21 '23 at 15:22
This is the only thing I got. – whatsinthename Jul 21 '23 at 16:09 — whatsinthename, Jul 21 '23 at 16:09

score 0 · Answer 1 · answered Jul 21 '23 at 18:25

0

Replace the "content" key in 200 response to something else like say "message" etc. and it will work. It seems like you cannot use "content" as a key in responses as OpenAPI may be using it for parsing. For example:

responses={**responses, 200: {"message": "valid"}}

answered Jul 21 '23 at 18:25

Rishi Mehta

399
3
10

I will try it out and let you know. – whatsinthename Jul 23 '23 at 07:26

Fast API response codes not working as expected

1 Answers1